Nonwoven Fabrics with Improved Haptics and Mechanical Properties

ABSTRACT

A multicomponent fiber for nonwovens and methods for making and using same. The multicomponent fiber can include a first component comprising a first polypropylene having a MFR of at least 30 dg/min and a second polypropylene having a MFR of less than 20 dg/min. The multicomponent fiber can further include a second component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and about 10 wt % to about 30 wt % of one or more alpha-olefin derived units, based on a total weight of the elastomer, wherein the propylene-based elastomer has a MFR of at least 40 dg/min and a heat of fusion (Hi) of about 3 J/g to about 75 J/g, as determined by DSC.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. Ser. No. 63/116,027, filed Nov. 19, 2020, which is incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments of the present invention generally relate to nonwovens and fibers for making nonwovens. More particularly, embodiments of the present invention generally relate to multicomponent fibers for making nonwovens.

BACKGROUND OF THE INVENTION

Synthetic fibers and nonwoven fabrics often lack a soft feel or “hand” like natural fibers and fabrics. The different aesthetic feeling is due to the lack of “loft” or “bulk” in synthetic materials, that is, a space-filling characteristic of natural fibers. Natural fibers are often not planar materials, and rather they exhibit some crimp or texture in three-dimensions that allow for space between fibers. Natural fibers can often be laid onto a plane and have a surface projecting from that plane, which are “3-dimensional.”

Synthetic fibers, however, are essentially planar, thus lacking the loft and feel of natural fibers. There are a number of methods to impart “bulkiness” or “loft” to synthetic fibers or fabrics, including mechanical treatments such as crimping, air jet texturing, or pleating. These techniques are not easy to apply to spunbond nonwoven fabrics in cost-effective ways.

Other attempts to increase “bulkiness” or “loft” involve “bicomponent” fibers that include two dissimilar polymers arranged in an organized spatial arrangement such as “side-by-side” or “sheath and core” within individual fibers. There is still a need, however, for bicomponent fibers that have better loft and softness, without sacrificing strength.

SUMMARY OF THE INVENTION

A multicomponent fiber for nonwovens and methods for making a fiber for fabrics with suitable thickness and softness are provided. The multicomponent fiber can include a first fiber component comprising a first polypropylene having a melt flow rate (MFR) of at least 30 dg/min and a second polypropylene having a MFR of less than 20 dg/min. The multicomponent fiber can further include a second fiber component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and about 10 wt % to about 30 wt % of one or more alpha-olefin derived units, based on a total weight of the elastomer, wherein the propylene-based elastomer has a MFR of at least 40 dg/min and a heat of fusion (Hf) of about 3 J/g to about 75 J/g, as determined by DSC.

The method for making a fiber for fabrics with suitable thickness and softness can include forming a first polymer composition comprising a first polypropylene having a MFR of at least 30 dg/min and a second polypropylene having a MFR of less than 20 dg/min. A second polymer composition can then be formed, the second polymer composition comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and about 10 wt % to about 30 wt % of one or more alpha-olefin derived units, based on a total weight of the elastomer and having a MFR of at least 40 dg/min and a heat of fusion (Hf) of about 3 J/g to about 75 J/g, as determined by DSC. A plurality of fibers from the first polymer composition and the second polymer composition in a side by side configuration can be formed, and a fabric can be made from the plurality of fibers. The fabric can have a contact thickness of at least 0.40 mm, a total hand of less than 20 g, and a MD and CD tensile of at least 8 N/5 cm.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. It is emphasized that the figures are not necessarily to scale and certain features and certain views of the figures can be shown exaggerated in scale or in schematic for clarity and/or conciseness.

FIG. 1 depicts a graphical representation of complex viscosity (Pa*s) versus temperature (° C.) for various samples prepared in accordance with one or more embodiments provided herein.

FIG. 2 depicts a graphical representation of Tan Delta versus temperature (° C.) for the samples prepared in accordance with one or more embodiments provided herein.

FIG. 3 is a cross-sectional schematic view of a loft characterization test method, in accordance with one or more embodiments of the invention.

FIG. 4 is plot of Normal Force vs. Gap for a variety of materials, as generated by a loft characterization test method, in accordance with one or more embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure can repeat reference numerals and/or letters in the various embodiments and across the figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations. Moreover, the formation of a first feature over or on a second feature in the description that follows can include embodiments in which the first and second features are formed in direct contact, and can also include embodiments in which additional features can be formed interposing the first and second features, such that the first and second features are not in direct contact. Finally, the embodiments presented below can be combined in any combination of ways, i.e., any element from one embodiment can be used in any other embodiment, without departing from the scope of the disclosure.

Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities can refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.”

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” The phrase “consisting essentially of” means that the described/claimed composition does not include any other components that will materially alter its properties by any more than 5% of that property, and in any case does not include any other component to a level greater than 3 mass %. The phrase “consisting of” means that the described/claimed composition does not include any other components.

The term “or” is intended to encompass both exclusive and inclusive cases, i.e., “A or B” is intended to be synonymous with “at least one of A and B,” unless otherwise expressly specified herein. The indefinite articles “a” and “an” refer to both singular forms (i.e., “one”) and plural referents (i.e., one or more) unless the context clearly dictates otherwise. For example, embodiments using “an olefin” include embodiments where one, two, or more olefins are used, unless specified to the contrary or the context clearly indicates that only one olefin is used.

The term “wt %” means percentage by weight, “vol %” means percentage by volume, “mol %” means percentage by mole, “ppm” means parts per million, and “ppm wt” and “wppm” are used interchangeably and mean parts per million on a weight basis. All concentrations herein, unless otherwise stated, are expressed on the basis of the total amount of the composition in question.

A detailed description of a multicomponent fiber for nonwovens and methods for using the same will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references to the “invention” may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will now be described in greater detail below, including specific embodiments, versions and examples, but the inventions are not limited to these embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the inventions, when the information in this disclosure is combined with publicly available information and technology.

The multicomponent fiber can include at least a first fiber component and a second fiber component. The first fiber component can include at least one low MFR (i.e. 20 MFR or less) polymer and at least one higher MFR polymer (i.e. 30 MFR or more). The second fiber component can include at least one higher MFR polymer (i.e. 30 MFR or more) and at least least one propylene-based elastomer (PBE). The low MFR polymer(s) and the higher MFR polymer(s) can be polyolefins and/or polyolefin copolymers. In certain embodiments, both the low MFR polymer(s) and the higher MFR polymer(s) are polypropylenes (PPs). In certain embodiments, the higher MFR polymer in the second fiber component is the same higher MFR polymer in the first fiber component.

It has been surprisingly discovered that blending at least one low MFR (i.e. 20 MFR or less) polymer with at least one higher MFR polymer (i.e. 30 MFR or more) and using that blend on one side of a side-by-side fiber with the same higher MFR polymer(s) blended with at least one propylene-based elastomer (PBE) on the other side of the fiber can produce fabrics that not only have increased z-directional thickness but also significantly increased softness. It was also surprisingly discovered that these PBE modified fabrics are stronger than fabrics without the PBE. Indeed, the produced fabrics provide exceptional softness while maintaining a high tensile strength.

By “low MFR” it is meant 20 dg/min or less, as measured according to ASTM D-1238 (2.16 kg weight @ 230° C.). For example, the MFR of a low MFR polymer can be 20 dg/min or less, 18 dg/min or less, or 16 dg/min or less. The MFR of a low MFR polymer can also range from a low of about 3, 5, or 7 dg/min to a high of about 15, 18, or 20 dg/min.

By “higher MFR” it is meant 30 dg/min or more, as measured according to ASTM D-1238 (2.16 kg weight @ 230° C.). For example, the MFR of a high MFR polymer can be 35 dg/min or more, 40 dg/min or more, or 45 dg/min or more. The MFR of a high MFR polymer can also range from a low of about 25, 28, or 33 dg/min to a high of about 38, 48, or 58 d g/min.

As used herein, the terms “monomer” or “comonomer,” can refer to the monomer used to form the polymer, e.g., the unreacted chemical compound in the form prior to polymerization, and can also refer to the monomer after it has been incorporated into the polymer, also referred to herein as a “[monomer]-derived unit”.

The term “copolymer” is meant to include polymers having two or more monomers, optionally, with other monomers, and may refer to interpolymers, terpolymers, etc. The term “polymer” as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc., and alloys and blends thereof. The term “polymer” as used herein also includes impact, block, graft, random, and alternating copolymers. The term “polymer” shall further include all possible geometrical configurations unless otherwise specifically stated. Such configurations may include isotactic, syndiotactic and random symmetries.

The term “polymer” refers to any two or more of the same or different repeating units/mer units or units. The term “homopolymer” refers to a polymer having units that are the same. The term “copolymer” refers to a polymer having two or more units that are different from each other, and includes terpolymers and the like. The term “terpolymer” refers to a polymer having three units that are different from each other. The term “different” as it refers to units indicates that the units differ from each other by at least one atom or are different isomerically. Likewise, the definition of polymer, as used herein, includes homopolymers, copolymers, and the like. By way of example, when a copolymer is said to have a “propylene” content of 10 wt % to 30 wt %, it is understood that the repeating unit/mer unit or simply unit in the copolymer is derived from propylene in the polymerization reaction and the derived units are present at 10 wt % to 30 wt %, based on a weight of the copolymer.

The term “elastomer” shall mean any polymer exhibiting some degree of elasticity, where elasticity is the ability of a material that has been deformed by a force (such as by stretching) to return at least partially to its original dimensions once the force has been removed.

The terms “α-olefin” or “alpha olefin” refers to any linear or branched compound of carbon and hydrogen having at least one double bond between the α and β carbon atoms. For purposes of this specification and the claims appended thereto, when a polymer or copolymer is referred to as including an α-olefin, e.g., poly-α-olefin, the α-olefin present in such polymer or copolymer is the polymerized form of the α-olefin.

Polypropylene

The term “polypropylene,” as used herein, includes homopolymers and copolymers of propylene or mixtures thereof. Products that include one or more propylene monomers polymerized with one or more additional monomers may be more commonly known as random copolymers (RCP) or impact copolymers (ICP). Impact copolymers may also be known in the art as heterophasic copolymers. “Propylene-based,” as used herein, is meant to include any polymer containing propylene, either alone or in combination with one or more comonomers, in which propylene is the major component (e.g., greater than 50 wt % propylene).

“Reactor grade,” as used herein, means a polymer that has not been chemically or mechanically treated or blended after polymerization in an effort to alter the polymer's average molecular weight, molecular weight distribution, or viscosity. Particularly excluded from those polymers described as reactor grade are those that have been visbroken or otherwise treated or coated with peroxide or other prodegradants. For the purposes of this disclosure, however, reactor grade polymers include those polymers that are reactor blends.

“Reactor blend,” as used herein, means a highly dispersed and mechanically inseparable blend of two or more polymers produced in situ as the result of sequential or parallel polymerization of one or more monomers with the formation of one polymer in the presence of another in series reactors, or by solution blending polymers made separately in parallel reactors. Reactor blends may be produced in a single reactor, a series of reactors, or parallel reactors and are reactor grade blends. Reactor blends may be produced by any polymerization method, including batch, semi-continuous, or continuous systems. Particularly excluded from “reactor blend” polymers are blends of two or more polymers in which the polymers are blended ex situ, such as by physically or mechanically blending in a mixer, extruder, or other similar device.

“Visbreaking,” as used herein, is a process for reducing the molecular weight of a polymer by subjecting the polymer to chain scission. The visbreaking process also increases the MFR of a polymer and may narrow its molecular weight distribution. Several different types of chemical reactions can be employed for visbreaking propylene-based polymers. An example is thermal pyrolysis, which is accomplished by exposing a polymer to high temperatures, e.g., in an extruder at 270° C. or higher. Other approaches are exposure to powerful oxidizing agents and exposure to ionizing radiation. Another method of visbreaking is the addition of a prodegradant to the polymer. A prodegradant is a substance that promotes chain scission when mixed with a polymer, which is then heated under extrusion conditions. Examples of prodegradants that may be used include peroxides, such as alkyl hydroperoxides and dialkyl peroxides. These materials, at elevated temperatures, initiate a free radical chain reaction resulting in scission of polypropylene molecules. The terms “prodegradant” and “visbreaking agent” are used interchangeably herein. Polymers that have undergone chain scission via a visbreaking process are said herein to be “visbroken.” Such visbroken polymer grades, particularly polypropylene grades, are often referred to in the industry as “controlled rheology” or “CR” grades.

“Catalyst system,” as used herein, means the combination of one or more catalysts with one or more activators and, optionally, one or more support compositions. An “activator” is any compound(s) or component(s) capable of enhancing the ability of one or more catalysts to polymerize monomers to polymers.

The weight average molecular weight (Mw) of the polypropylene can be between 50,000 to 3,000,000 g/mol, or from 90,000 to 500,000 g/mol, with a molecular weight distribution (MWD, equal to weight average molecular weight divided by number average molecular weight, Mw/Mn) within the range from 1.5 to 2.5 or 3.0 or 4.0 or 5.0 or 20.0. The polypropylene can have an MFR (2.16 kg/230° C.) within the range from 10 or 15 or 18 to 30 or 35 or 40 or 50 dg/min.

Propylene-Based Elastomer (PBE)

The PBE contains propylene and from about 5 wt % to about 30 wt % of one or more alpha-olefin derived units, for example, ethylene and/or C4-C12 α-olefins. In some examples, the alpha-olefin derived units, or comonomer, may be ethylene, butene, pentene, hexene, 4-methyl-1-pentene, octene, or decene. In one or more examples, the comonomer is ethylene. In some embodiments, the PBE consists essentially of propylene and ethylene, or consists only of propylene and ethylene. Some of the embodiments described below are discussed with reference to ethylene as the comonomer, but the embodiments are equally applicable to PBEs with other α-olefin comonomers. In this regard, the copolymers may simply be referred to as PBE with reference to ethylene as the α-olefin.

The PBE may include at least about 5 wt %, at least about 6 wt %, at least about 7 wt %, at least about 8 wt %, at least about 9 wt %, at least about 10 wt %, at least about 12 wt %, or at least about 15 wt %, α-olefin-derived units, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units. The PBE may include up to about 30 wt %, up to about 25 wt %, up to about 22 wt %, up to about 20 wt %, up to about 19 wt %, up to about 18 wt %, or up to about 17 wt %, α-olefin-derived units, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units. In some embodiments, the PBE may contain from about 5 wt % to about 30 wt %, from about 6 wt % to about 25 wt %, from about 7 wt % to about 20 wt %, from about 10 wt % to about 19 wt %, from about 12 wt % to about 18 wt %, or from about 15 wt % to about 17 wt %, α-olefin-derived units, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units.

The PBE may include at least about 70 wt %, at least about 75 wt %, at least about 78 wt %, at least about 80 wt %, at least about 81 wt %, at least about 82 wt %, or at least about 83 wt %, propylene-derived units, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin derived units. The PBE may include up to about 95 wt %, up to about 94 wt %, up to about 93 wt %, up to about 92 wt %, up to about 91 wt %, up to about 90 wt %, up to about 88 wt %, or up to about 85 wt %, propylene-derived units, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin derived units.

The PBE may be characterized by a melting point (Tm), which can be determined by differential scanning calorimetry (DSC). For purposes herein, the maximum of the highest temperature peak is considered to be the melting point of the polymer. A “peak” in this context is defined as a change in the general slope of the DSC curve (heat flow versus temperature) from positive to negative, forming a maximum without a shift in the baseline where the DSC curve is plotted so that an endothermic reaction would be shown with a positive peak. The Tm of the PBE (as determined by DSC) may be less than 120° C., less than 115° C., less than 110° C., or less than 105° C.

The PBE may be characterized by its heat of fusion (Hf), as determined by DSC. The PBE may have an Hf that is at least about 0.5 J/g, at least about 1.0 J/g, at least about 1.5 J/g, at least about 3.0 J/g, at least about 4.0 J/g, at least about 5.0 J/g, at least about 6.0 J/g, or at least about 7.0 J/g. The PBE may be characterized by an Hf of less than 75 J/g, or less than 70 J/g, or less than 60 J/g, or less than 50 J/g. In one or more examples, the PBE has a melting temperature of less than 120° C. and a heat of fusion of less than 75 J/g.

The PBE can have a triad tacticity of three propylene units (mm tacticity), as measured by 13 C nuclear magnetic resonance (NMR), of 75% or greater, 80% or greater, 85% or greater, 90% or greater, 92% or greater, 95% or greater, or 97% or greater. For example, the triad tacticity may range from about 75% to about 99%, from about 80% to about 99%, from about 85% to about 99%, from about 90% to about 99%, from about 90% to about 97%, or from about 80% to about 97%. Triad tacticity may be determined by the methods described in U.S. Pat. No. 7,232,871.

The PBE may have a tacticity index m/r ranging from a lower limit of 4 or 6 to an upper limit of 8 or 10 or 12. The tacticity index, expressed herein as “m/r”, is determined by 13 C NMR. The tacticity index, m/r, is calculated as defined by H. N. Cheng in Vol. 17, MACROMOLECULES, pp. 1950-1955 (1984), incorporated herein by reference. The designation “m” or “r” describes the stereochemistry of pairs of contiguous propylene groups, “m” referring to meso, and “r” to racemic. An m/r ratio of 1.0 generally describes a syndiotactic polymer, and an m/r ratio of 2.0 describes an atactic material.

The PBE may have a percent crystallinity of about 0.5% to about 40%, from about 1% to about 30%, or from about 5% to about 25%, determined according to DSC procedures. Crystallinity may be determined by dividing the Hf of a sample by the Hf of a 100% crystalline polymer, which is assumed to be 189 J/g for isotactic polypropylene.

The PBE may have a density of about 0.84 g/cm3 to about 0.92 g/cm3, from about 0.85 g/cm3 to about 0.90 g/cm3, or from about 0.85 g/cm3 to about 0.87 g/cm3 at room temperature (about 23° C.), as measured per the ASTM D-1505 test method.

The PBE can have a melt index (MI, of less than or equal to about 100 dg/min, less than or equal to about 555 dg/min, less than or equal to about 25 dg/min, less than or equal to about 10 dg/min, less than or equal to about 8.0 dg/min, less than or equal to about 5.0 dg/min, or less than or equal to about 3.0 dg/min, as measured per ASTM D-1238 (2.16 kg @ 190° C.).

The PBE may have a MFR, as measured according to ASTM D-1238 (2.16 kg weight @ 230° C.), greater than 0.5 dg/min, greater than 1.0 dg/min, greater than 1.5 dg/min, greater than 2.0 dg/min, or greater than 2.5 dg/min. The PBE may have an MFR less than 100 dg/min, less than 55 dg/min, less than 25 dg/min, less than 15 dg/min, less than 10 dg/min, less than 7 dg/min, or less than 5 dg/min. In some embodiments, the PBE may have an MFR from about 0.5 to about 10 dg/min, from about 1.0 to about 7 dg/min, or from about 1.5 to about 5 dg/min.

The PBE may have a g′ index value of 0.95 or greater, or at least 0.97, or at least 0.99, wherein g′ is measured at the weight average molecular weight (Mw) of the polymer using the intrinsic viscosity of isotactic polypropylene as the baseline. For use herein, the g′ index is defined as: g′=ηb/η1, where ηb is the intrinsic viscosity of the polymer and η1 is the intrinsic viscosity of a linear polymer of the same viscosity-averaged molecular weight (Mv) as the polymer. η1=KMvα, K and α are measured values for linear polymers and should be obtained on the same instrument as the one used for the g′ index measurement.

The PBE may have a Mw, as measured by DRI, of about 50,000 to about 1,000,000 g/mol, or from about 75,000 to about 500,000 g/mol, from about 100,000 to about 350,000 g/mol, from about 125,000 to about 300,000 g/mol, from about 150,000 to about 275,000 g/mol, or from about 200,000 to about 250,000 g/mol.

The PBE may have a Mn) as measured by DRI, of about 5,000 to about 500,000 g/mol, from about 10,000 to about 300,000 g/mol, from about 50,000 to about 250,000 g/mol, from about 75,000 to about 200,000 g/mol, or from about 100,000 to about 150,000 g/mol.

The PBE may have a z-average molecular weight (Mz), as measured by MALLS, of about 50,000 to about 1,000,000 g/mol, or from about 75,000 to about 500,000 g/mol, or from about 100,000 to about 400,000 g/mol, from about 200,000 to about 375,000 g/mol, or from about 250,000 to about 350,000 g/mol.

The MWD of the PBE may be from about 0.5 to about 20, from about 0.75 to about 10, from about 1.0 to about 5, from about 1.5 to about 4, or from about 1.8 to about 3.

Optionally, the PBE may also include one or more dienes. The term “diene” is defined as a hydrocarbon compound that has two unsaturation sites, e.g., a compound having two double bonds connecting carbon atoms. Depending on the context, the term “diene” as used herein refers broadly to either a diene monomer prior to polymerization, e.g., forming part of the polymerization medium, or a diene monomer after polymerization has begun (also referred to as a diene monomer unit or a diene-derived unit). In some embodiments, the diene may be selected from 5-ethylidene-2-norbornene (ENB); 1,4-hexadiene; 5-methylene-2-norbornene (MNB); 1,6-octadiene; 5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene; 1,4-cyclohexadiene; vinyl norbornene (VNB); dicyclopentadiene (DCPD), and combinations thereof. In embodiments where the PBE composition contains a diene, the diene may be present at from 0.05 wt % to about 6 wt %, from about 0.1 wt % to about 5.0 wt %, from about 0.25 wt % to about 3.0 wt %, from about 0.5 wt % to about 1.5 wt %, diene-derived units, where the percentage by weight is based upon the total weight of the propylene-derived, α-olefin derived, and diene-derived units.

Optionally, the PBE may be grafted (e.g., “functionalized”) using one or more grafting monomers. As used herein, the term “grafting” denotes covalent bonding of the grafting monomer to a polymer chain of the PBE. The grafting monomer can be or include at least one ethylenically unsaturated carboxylic acid or acid derivative, such as an acid anhydride, ester, salt, amide, imide, or acrylates. Illustrative grafting monomers include, but are not limited to, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, maleic anhydride, 4-methyl cyclohexene-1,2-dicarboxylic acid anhydride, bicyclo(2.2.2)octene-2,3-dicarboxylic acid anhydride, 1,2,3,4,5,8,9,10-octahydronaphthalene-2,3-dicarboxylic acid anhydride, 2-oxa-1,3-diketospiro(4.4)nonene, bicyclo(2.2.1)heptene-2,3-dicarboxylic acid anhydride, maleopimaric acid, tetrahydrophthalic anhydride, norbornene-2,3-dicarboxylic acid anhydride, nadic anhydride, methyl nadic anhydride, himic anhydride, methyl himic anhydride, and 5-methylbicyclo(2.2.1)heptene-2,3-dicarboxylic acid anhydride. Other suitable grafting monomers include methyl acrylate and higher alkyl acrylates, methyl methacrylate and higher alkyl methacrylates, acrylic acid, methacrylic acid, hydroxy-methyl methacrylate, hydroxyl-ethyl methacrylate and higher hydroxy-alkyl methacrylates and glycidyl methacrylate. Maleic anhydride is a grafting monomer. In embodiments, the graft monomer can be or include maleic anhydride, and the maleic anhydride concentration in the grafted polymer is in the range of about 1 wt % to about 6 wt %, such as at least about 0.5 wt %, or at least about 1.5 wt %.

In some embodiments, the PBE is a reactor blended polymer as defined herein. That is, the PBE is a reactor blend of a first polymer component and a second polymer component. Thus, the comonomer content of the PBE can be adjusted by adjusting the comonomer content of the first polymer component, adjusting the comonomer content of second polymer component, and/or adjusting the ratio of the first polymer component to the second polymer component present in the PBE.

In embodiments where the PBE is a reactor blended polymer, the α-olefin content of the first polymer component may be greater than 5 wt % α-olefin, greater than 7 wt % α-olefin, greater than 10 wt % α-olefin, greater than 12 wt % α-olefin, greater than 15 wt % α-olefin, or greater than 17 wt % α-olefin, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units of the first polymer component. The α-olefin content of the first polymer component may be less than 30 wt % α-olefin, less than 27 wt % α-olefin, less than 25 wt % α-olefin, less than 22 wt % α-olefin, less than 20 wt % α-olefin, or less than 19 wt % α-olefin, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units of the first polymer component. In some embodiments, the α-olefin content of the first polymer component may range from 5 wt % to 30 wt % α-olefin, from 7 wt % to 27 wt % α-olefin, from 10 wt % to 25 wt % α-olefin, from 12 wt % to 22 wt % α-olefin, from 15 wt % to 20 wt % α-olefin, or from 17 wt % to 19 wt % α-olefin. In some examples, the first polymer component contains or comprises propylene and ethylene, and in some embodiments the first polymer component consists only of propylene and ethylene derived units.

In embodiments where the PBE is a reactor blended polymer, the α-olefin content of the second polymer component may be greater than 1.0 wt % α-olefin, greater than 1.5 wt % α-olefin, greater than 2.0 wt % α-olefin, greater than 2.5 wt % α-olefin, greater than 2.75 wt % α-olefin, or greater than 3.0 wt % α-olefin, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units of the second polymer component. The α-olefin content of the second polymer component may be less than 10 wt % α-olefin, less than 9 wt % α-olefin, less than 8 wt % α-olefin, less than 7 wt % α-olefin, less than 6 wt % α-olefin, or less than 5 wt % α-olefin, where the percentage by weight is based upon the total weight of the propylene-derived and α-olefin-derived units of the second polymer component. In some embodiments, the α-olefin content of the second polymer component may range from 1.0 wt % to 10 wt % α-olefin, or from 1.5 wt % to 9 wt % α-olefin, or from 2.0 wt % to 8 wt % α-olefin, or from 2.5 wt % to 7 wt % α-olefin, or from 2.75 wt % to 6 wt % α-olefin, or from 3 wt % to 5 wt % α-olefin. In some examples, the second polymer component contains propylene and ethylene, and in some embodiments the first polymer component consists only of propylene and ethylene derived units.

In certain embodiments, the PBE contains propylene-derived units and about 5 wt % to about 30 wt % of α-olefin-derived units and has a melting temperature of less than 120° C. and a heat of fusion of less than 75 J/g.

In certain embodiments, the PBE contains propylene-derived units and about 10 wt % to about 30 wt % of one or more alpha-olefin derived units, and has a MFR of at least 40 dg/min and a heat of fusion (Hf) of about 3 J/g to about 75 J/g, as determined by DSC.

In embodiments where the PBE is a reactor blended polymer, the PBE may contain from 1 wt % to 25 wt % of the second polymer component, from 3 wt % to 20 wt % of the second polymer component, from 5 wt % to 18 wt % of the second polymer component, from 7 wt % to 15 wt % of the second polymer component, or from 8 wt % to 12 wt % of the second polymer component, based on the weight of the PBE. The PBE may contain from 75 wt % to 99 wt % of the first polymer component, from 80 wt % to 97 wt % of the first polymer component, from 85 wt % to 93 wt % of the first polymer component, or from 82 wt % to 92 wt % of the first polymer component, based on the weight of the PBE.

In one or more embodiments, the PBE contains a reactor blend of a first polymer component and a second polymer component. The first polymer component contains propylene and an α-olefin and has an α-olefin content of greater than 5 wt % to less than 30 wt % of the α-olefin, based on the total weight of the propylene-derived and α-olefin derived units of the first polymer component. The second polymer component contains propylene and α-olefin and has an α-olefin content of greater than 1 wt % to less than 10 wt % of the α-olefin, based on the total weight of the propylene-derived and α-olefin derived units of the second polymer component. In one or more examples, the first polymer component has an α-olefin content of about 10 wt % to about 25 wt % of the α-olefin, based on the total weight of the propylene-derived and α-olefin derived units of the first polymer component. The second polymer component has an α-olefin content of greater than 2 wt % to less than 8 wt % of the α-olefin, based on the total weight of the propylene-derived and α-olefin derived units of the second polymer component. In other examples, the PBE contains about 1 wt % to about 25 wt % of the second polymer component and about 75 wt % to about 99 wt % of the first polymer component, based on the weight of the PBE.

The PBE may be prepared by any suitable means as known in the art. The PBE can be prepared using homogeneous conditions, such as a continuous solution polymerization process, using a metallocene catalyst. In some embodiments, the PBE are prepared in parallel solution polymerization reactors, such that the first reactor component is prepared in a first reactor and the second reactor component is prepared in a second reactor, and the reactor effluent from the first and second reactors are combined and blended to form a single effluent from which the final PBE is separated. Exemplary methods for the preparation of PBEs may be found in U.S. Pat. Nos. 6,881,800; 7,803,876; 8,013,069; and 8,026,323 and PCT Publications WO 2011/087729; WO 2011/087730; and WO 2011/087731.

As used herein, a “nonwoven fabric” (or “fabric” as used herein) is a textile structure (e.g., a sheet, web or batt) of directionally or randomly orientated fibers, without a yarn being first made. The fabrics described herein comprise a network of fibers or continuous filament yarns strengthened by mechanical, chemical, or thermally interlocking processes. A “multilayer fabric” comprises at least two fabric layers; as used herein, a “layer” refers to a fabric. A “fiber” is a material whose length is very much greater than its diameter or breadth; the average diameter is on the order of 0.01 to 200 μm, and comprises natural and/or synthetic materials.

As used herein, “bound” (or “bond” or “adhered”) means that two or more fabrics, or a plurality of fibers, is secured to one another through (i) the inherent tendency of the molten or non-molten materials' ability to adhere through chemical interactions and/or (ii) the ability of the molten or non-molten fibers and/or fabric to entangle with the fibers comprising another material to generate a linkage between the fibers or fabrics. Adhesives may be used to facilitate bonding of fabric layers, but in a particular embodiment, adhesives are absent from the fabric layers (not used to bond the fibers of a fabric) described herein; and in another embodiment, absent from the multilayer fabrics (not used to bond adjacent fabric layers) described herein. Examples of adhesives include those comprising low weight average molecular weight (<80,000 g/mole) polyolefins, polyvinyl acetate polyamide, hydrocarbon resins, natural asphalts, styrenic rubbers, and blends thereof.

“Spunbond” fabrics are filament sheets made through an integrated process of spunbonding, which includes the steps of spinning the molten polymer, air attenuation, deposition (on a drum or other moving base to allow formation of the web, or onto another fabric(s)) and bonding. The method of spunbonding is well known and described generally in, for example, POLYPROPYLENE HANDBOOK 314-324 (E. Moore, Hanser Verlag, 1996). Such fibers range from 5 to 150 μm in average diameter in certain embodiments, and within a range of 10 to 40 or 50 or 100 μm in particular embodiments. A combination of thickness, fiber fineness (denier), and number of fibers per unit area determines the fabric basis weight which ranges from 8 or 10 or 15 to 50 or 80 or 120 or 400 or 800 g/m² in particular embodiments. Most spunbonded processes yield a fabric having planar-isotropic properties owing to the random laydown of the fibers. Spunbonded fabrics are generally nondirectional and can be cut and used without concern for higher stretching in the bias direction or unraveling at the edges. It is possible to produce nonisotropic properties by controlling the orientation of the fibers in the web during laydown. Fabric thickness varies from 0.1 to 4.0 mm, and within the range from 0.15 to 1.5 mm in particular embodiments. The method of bonding affects the thickness of the sheets, as well as other characteristics. In particular embodiments, adhesives are absent as bonding agents; thermal-type bonding is preferred. Fiber webs bonded by thermal calendering are thinner than the same web that has been needle-punched, because calendering compresses the structure through pressure, whereas needle-punching moves fibers from the x-y plane of the fabric into the z (thickness) direction.

One area in which nonwovens find use is in the hygiene segment. Articles such as diapers, adult incontinence, and feminine hygiene products. Nonwovens are used in various components of these articles as topsheets, backsheets, acquisition distribution layers, bellybands and legcuffs. For such articles, the quality of softness, though not well defined, is of importance. Nonwovens with improved thickness or loft enhances the perception of softness for the individual wearing the article, or for those who might handle the article directly.

EXAMPLES

Embodiments discussed and described herein can be further described with the following examples. Although the following examples are directed to specific embodiments, they are not to be viewed as limiting in any specific respect.

Two (2) multicomponent fibers were prepared from a first fiber component and a second fiber component, according to one or more embodiments provided above. Another two (2) comparative examples are provided to better show the surprising and significant differences the addition of the PBE makes and the differences in MFR between the polymers on one side of the fiber. Table 1 summarizes the physical characteristics of the first fiber component, and Table 2 summarizes the physical characteristics of the second fiber component. Table 3 summarizes the fiber components that were prepared and tested.

TABLE 1 First Fiber Component PP1 PP2 MWD 3.0 3.0 Mw g/mol 180000 230,000 Mn g/mol 55000 85,000 Mz g/mol 380000 490,000 MFR dg/min 36 13 Tm ° C. 159 165 Tc ° C. 110 109.8 Heat of Fusion (Hf) J/g 101 90.8 Triad Tacticity % 0.96

TABLE 2 Second Fiber Component PP1 PBE MWD 3.0 2.5 Mw g/mol 180,000 119,000 Mn g/mol 55,000 45,000 Mz g/mol 380,000 191,000 MFR dg/min 36 48 Tm ° C. 159 60.5 Tc ° C. 110 Heat of Fusion (Hf) J/g 101 18.6 Triad Tacticity % 0.96

TABLE 3 Fiber Components First Fiber Second Fiber 1^(st) Fiber Comp// Component Slip Component 2^(nd) Fiber Comp (wt %) (ppm) (wt %) Ratio Comp. PP1 0 60% PP1 + 80 20 Ex. 11 40% PP2 Comp. PP1 500 60% PP1 + 80 20 Ex. 22 40% PP2 Ex. 1 80% PP1 + 0 60% PP1 + 80 20 20% PBE 40% PP2 Ex. 2 80% PP1 + 1000 60% PP1 + 80 20 20% PBE 40% PP2

For Comp. Ex. 22, the First Fiber Component includes 500 ppm of an erucamide slip additive. The slip additive is added as a masterbatch, SCC-88953 sourced from Standridge Color Corporation, which has approximately 10% loading of active erucamide component in a polypropylene base resin. For Ex. 2, the First Fiber Component includes 1000 ppm of the erucamide slip additive, included via the SCC-88953 masterbatch.

TABLE 4 Fabric Characteristics CD MD CD MD Bonding Thru Cabin Basis Total Elong Elong Tensile Tensile Temps. put Pressure Thickness Weight Hand at Peak at Peak at Peak at Peak E/S (kg/h) (Pa) (mm) (g/sqm) (g) (%) (%) (N/5 cm) (N/5 cm) (° C.) Comp. Ex. 11 220 4200 0.48 28.0 21.7 128.5 108.2 17.1 29.7 135/135 Comp. Ex. 22 220 4200 0.43 25.4 14.0 91.7 73.5 16.5 29.3 135/135 Ex. 1 220 4200 0.55 28.9 9.6 213.3 171.5 12.2 22.1 135/135 Ex. 2 220 4200 0.53 28.6 9.1 199.2 177.6 14.8 27.2 135/135

TABLE 5 Melt Analysis of various formulations Rheological PP1 Fiber PP2 Fiber 1st Melt 2nd Melt Crystallization Crystallization PBE Component Component Temperature Temperature Temperature Temperature (%) (%) (%) (C.) (C.) (C.) Tc, rheol (C.) 20 80 0 164.3 165.0 109.8 129.6 0 80 20 n/a n/a n/a 131.98

Crystallization via SAOS Rheology

Referring to Table 5, crystallization was monitored via SAOS rheology, where the sample was cooled down from the molten state (at 190° C.) at a fixed cooling rate using a 25 mm parallel plate configuration on an ARES 2001 (TA Instruments) controlled strain rheometer. Sample test disks (25 mm diameter, 2.5 mm thickness) were made with a Carver Laboratory press at 190° C. Samples were allowed to sit without pressure for approximately 3 minutes in order to melt and then held under pressure for 3 minutes to compression mold the sample. The disks were originally approximately 2.5 mm thick; however, after sample trimming off the parallel plates, a gap of 1.9 mm between the plates was used. Thermal expansion of the tools was taken into account during SAOS testing to maintain a constant gap throughout the test. The sample was first heated from room temperature to 190° C. The sample was equilibrated at 190° C. (molten state) for 15 min to erase any prior thermal and crystallization history. The temperature was controlled reproducibly within ±0.5° C. The sample was then cooled from 190° C. at a constant cooling rate of 1° C./min and an angular frequency of 1 rad/s using a strain of 1% lying in the linear viscoelastic region. For termination of the experiment, a maximum torque criterion was used. Upon the onset of crystallization during the rheological test, the instrument goes into an overload condition when maximum torque is reached and the test is stopped automatically. All experiments were performed in a nitrogen atmosphere to minimize any degradation of the sample during rheological testing. Crystallization was observed by a steep/sudden increase of the complex viscosity and a steep/sudden (step-like) decrease of the Loss Tangent (tan δ) (i.e., a plot of complex viscosity vs. temperature and Loss Tangent vs. temperature depict a neck-like region of sudden change in the rheological properties due to occurrence of crystallization). The “onset crystallization temperature via rheology,” Tc,rheol is defined as the temperature at which a steep (i.e., neck-like) increase of the complex viscosity and a simultaneous steep decrease of tan δ is observed. The reproducibility of Tc,rheol, is within ±1° C.

Differential Scanning Calorimetry (DSC)

Peak crystallization temperature (Tc), peak melting temperature (Tm) and heat of fusion (Hf) were measured via DSCon pellet samples using a DSCQ200 (TA Instruments) unit. The DSC was calibrated for temperature using four standards (tin, indium, cyclohexane, and water). The heat flow of indium (28.46 J/g) was used to calibrate the heat flow signal. A sample of 3 to 5 mg of polymer, typically in pellet form, was sealed in a standard aluminum pan with flat lids and loaded into the instrument at room temperature. In the case of determination of and Tm corresponding to 10° C./min cooling and heating rates, the following procedure was used. The sample was first equilibrated at 25° C. and subsequently heated to 200° C. using a heating rate of 10° C./min (first heat). The sample was held at 200° C. for 5 min to erase any prior thermal and crystallization history. The sample was subsequently cooled down to 25° C. with a constant cooling rate of 10° C./min (first cool). The exothermic peak of crystallization (first cool) was determined via analysis using the TA Universal Analysis software. The sample was held isothermal at 25° C. for 10 min before being heated to 200° C. at a constant heating rate of 10° C./min (second heat). The endothermic peak of melting (second heat) was also analyzed using the TA Universal Analysis software and the Tm and Hf values were determined.

Z-direction thickness was measured using WSP 120.6 (05), option A, 0.5 kPa, using a contact time of 5 sec, and was recorded as an average over 3 samples. The contact thickness measurements were taken within one hour of fabric manufacturing.

Tensile properties of nonwoven fabrics such as tensile (peak) strength and % (peak) elongation in both machine (MD) and cross (CD) directions were measured according to standard method WSP 110.4 (05) with a gauge length of 200 mm and a testing speed of 100 mm/min, unless otherwise indicated. The width of the fabric specimen was 5 cm. For the tensile testing, an Instron machine was used (Model 5565) equipped with Instron Bluehill 2 (version 2.5) software for the data analysis.

Softness or “hand” as it is known in the art, is measured using the Thwing-Albert Instruments Co. Handle-O-Meter (Model 211-10-B/AERGLA). The quality of “hand” is considered to be the combination of resistance due to the surface friction and flexibility of a fabric material. The Handle-O-Meter measures the above two factors using an LVDT (Linear Variable Differential Transformer) to detect the resistance that a blade encounters when forcing a specimen of material into a slot of parallel edges. A 3½ digit digital voltmeter (DVM) indicates the resistance directly in gram force. The “total hand” of a given fabric is defined as the average of 8 readings taken on two fabric specimens (4 readings per specimen). For each test specimen (5 mm slot width), the hand is measured on both sides and both directions (MD and CD) and is recorded in grams. A decrease in “total hand” indicates the improvement of fabric softness.

Thickness, Compressibility, and Resiliency

Bulky nonwoven fabrics such as those disclosed herein can be differentiated from conventional nonwoven fabrics in terms of “loft”, which may be characterized as 1) the z-directional thickness of the fabric, and 2) how the fabric responds to compression. There is no standard test method to measure “loft”. Currently, handle-o-meter and contact thickness, discussed above, are used to characterize lofty nonwoven fabrics.

U.S. Pat. No. 9,826,877 discloses a test method for measuring compression and recovery of a makeup remover wipe (a nonwoven material saturated with lotion). Using an AMES Gage, the compressibility was determined by measuring the thickness of the wipe when compressed by presser feet of increasing weight, ranging from 0.5 oz. to 7.0 oz. The recovery of the wipe was measured by re-measuring the thickness of the wipe at the lowest, initial weight (0.5 oz) after completion of the compressibility test, and comparing this thickness value to the first, pre-compression measurement at 0.5 oz. Lower thicknesses for the second 0.5 oz measurement as compared to the first 0.5 oz measurement indicate less resiliency.

To characterize lofty nonwoven fabrics, the inventors have developed a test method that measures z-direction thickness, compressibility, and resiliency. A sample of material, such as a nonwoven fabric, is evaluated using a dynamic rotational rheometer. For the example measurements herein, an ARES-G2 from TA Instruments was used. Such a rheometer is typically used to evaluate properties of molten materials; however, for this method, a variety of natural and synthetic materials such as cotton, paper, and nonwoven fabrics may be evaluated.

A schematic cross-sectional view of a parallel-plate rheometer test setup 300 is illustrated in FIG. 3 . The test sample 302 is prepared by cutting circular discs of material having a diameter of about 30 mm. The test sample 302 is then placed between lower parallel plate 304 and upper parallel plate 306. The rheometer then compresses the sample 302 in a direction 308 normal to the surface of the sample 302 at a constant rate of 0.05 mm/sec. The compression rate may be selected to be suitable for the test sample material. In embodiments of the test method, the compression rate may be varied instead of constant, for example, the compression rate may decrease as compression increases. As the distance between the plates, gap 310, decreases, the force 308 normal to the surface of the nonwoven fabric (the “z-direction”) exerted on the plates by the sample is measured by the rheometer, producing a curve of Normal Force (N) vs. Gap (mm).

FIG. 4 illustrates Normal Force vs. Gap curves for several standard materials, including cotton, paper, and ultrasoft nonwoven, alongside curves for control samples Comp Ex. 11 and Comp Ex. 22, and inventive samples Ex. 1 and Ex. 2. The cotton standard is a high-loft, natural material. The paper standard is a material with no loft. The cotton standard and the paper standard were chosen for the plot to illustrate two extremes of very high loft (cotton) and no loft (paper). The ultrasoft standard is a nonwoven material that has been optimized for surface softness as opposed to loft; it is a nonwoven material triple layer spunbond monocomponent fiber made from a blend of 85 wt % PP3155, 15 wt % Vistamaxx 7020BF, both available from ExxonMobil Chemical Company, and 4000 ppm of erucamide slip agent. Softness is characterized using a Handle-o-meter and measuring coefficient of friction. Though softness preference vary by manufacturer and geography, the ultrasoft standard used herein represents a solution globally accepted by different brand owners for their premium product lines. Many nonwoven applications seek both high loft and softness, but achieving both has been a challenge. Fibers that achieve a high level of softness typically have a low modulus, which improves drape (Handle-o-meter); this low modulus makes it difficult for fabrics based on such fibers to achieve and maintain high loft. Fibers with a lower modulus will deflect under lower loads, as per Euler-Bernoulli beam theory; thus, in case of lower modulus fibers, the tridimensional structure may collapse under very low pressures and in certain cases even under the gravity field.

The Normal Force vs. Gap curves generated by this method can be evaluated further to characterize lofty materials. Gap distance (z-direction thickness) values can be compared at a constant Normal Force to evaluate comparative compressibility of different samples. Greater thickness indicates higher loft. The inventive nonwoven may have a thickness at a 0.5 N load that is 0.35 mm or greater, 0.38 mm or greater, 0.40 mm or greater or 0.44 mm or greater. At a 1 N load, the inventive nonwoven may have a thickness of 0.30 mm or greater, 0.35 mm or greater, or 0.38 mm or greater.

The area under the curve indicates the work of compression—the total work required to compress a sample to a given thickness. Greater work to compress indicates higher loft. The inventive nonwoven may have a work of compression of 10.5E-4 J or greater, 11.0E-4 J or greater, 12.0E-4 J or greater, or 13.0E-4 J or greater.

The slope of the curve at a given load indicates the stiffness of the material. The stiffness, measured in N/m, is similar to the spring constant in Hooke's law, and captures the compressibility of the material. Lower stiffness values indicates that at a given load, the sample gap distance decreases more for increasing normal force as compared to stiffer materials, which require higher loads for a decrease in gap distance. That is, lower stiffness indicates a loftier sample. The inventive nonwoven may have a stiffness at 1 N of less than 13 N/m, less than 12 N/m, or less than 11 N/m.

Resiliency is indicative of the retained thickness (or “loft”) of the material after long-lasting compression, simulating what happens when the fabric is wound in a roll form. To measure resiliency of a sample, fabric samples are subjected to a static load for an extended time period, with thickness (gap distance) measurements collected by a rheometer in plate-plate configuration both before and after the loading. For evaluating loft of nonwoven materials, a load of 4 kg and testing interval of 24 hours may be used. The load and test time may be selected to suit the sample material. As outlined in Eq. 1 and Eq. 2, resiliency is defined to be the difference in thickness (gap distance) measurements over the initial thickness (gap distance). Thickness retention is the complement of resiliency.

$\begin{matrix} {R = \frac{t_{0} - t_{l}}{t_{0}}} & (1) \end{matrix}$ $\begin{matrix} {T_{R} = {1 - R}} & (2) \end{matrix}$

Where:

-   -   R is the resiliency     -   T_(R) is the thickness retention     -   t₀ is the initial thickness     -   t_(l) is the thickness after compression

Table 6 shows the thickness, work of compression, and stiffness for Examples Ex. 1 and Ex. 2 of the inventive fabric as compared to various standards and comparative examples Comp. Ex. 11 and Comp. Ex. 22, as measured using the test method taught herein.

TABLE 6 Thickness and Compressibility of various materials Thickness Thickness Work of Stiffness (gap distance) (gap distance) Compression (Slope at Sample at 0.5N [mm] at 1N [mm] [J] 1N) [N/m] Cotton 0.59 0.53 13.9E−04 13 Standard Paper 0.12 0.11 1.81E−04 187.8 Standard Ultrasoft 0.18 0.16 5.05E−04 34.4 Standard Comp. 0.402 0.334 10.4E−04 11.527 Ex. 11 Comp. 0.359 0.324 9.05E−04 19.278 Ex. 22 Ex. 1 0.444 0.387 13.9E−04 11.592 Ex. 2 0.388 0.318 11.6E−04 10.220

Inventive samples Ex. 1 and Ex. 2 have thicknesses at 0.5N and 1N that are intermediate between the thicknesses of the paper standard (low loft) and cotton standard (high loft), and which indicate a significantly improved level of loft over that of the ultrasoft nonwoven standard.

The high loft cotton standard requires 13.9E-4 J of work to compress the sample. The inventive samples require a similar amount of work to compress—13.9E-4 J for Ex. 1 and 11.6E-4 J for Ex. 2. The comparative samples require a lower level of work to compress—10.4E-4 J for Comp. Ex. 11 and 9.05E-4 J for Comp. Ex. 22. The ultrasoft nonwoven standard requires significantly less work to compress—5.05E-4 J, less than half of that required by the inventive samples. The observed increase in work to compress of the inventive examples over that of the comparative examples is due to the presence of the PBE.

The differences in compression behavior can also be observed in FIG. 3 ; the curves of the cotton standard and inventive Ex. 1 and Ex. 2 have a more gradual transition from a lower stiffness region at higher gap distances to a higher stiffness region at smaller gap distances as compared to paper, the soft lean blend (ultrasoft standard), and comparative examples Comp. Ex. 11 and Comp Ex. 22, which show a more abrupt transition from lower stiffness at high gap distance to higher stiffness at low gap distance.

Unless otherwise noted, all fabric tests described above were performed at least 20 days from the day of fabric manufacturing to ensure equilibration of properties and account for any effects that may alter the fabric properties over time.

Spunbond Nonwoven Fabrics

Spunbonded nonwoven fabrics were produced on a single beam, Reicofil 4 (R4) line 1.1 m width each having a spinneret of 6800 holes with a hole (die) diameter of 0.6 mm For a detailed description of Reicofil spunbonding process, please refer to EP 1340843 or U.S. Pat. No. 6,918,750. The throughput per hole was variable as noted. The quench air temperature was 18° C. for all experiments. Under these conditions, fibers of 1 to 1.4 denier were produced, equivalent to a fiber diameter of 12 to 15 microns. Line speed varied as needed to obtain the nonwoven at its targeted fabric basis weight for all examples of 25 g/m² (gsm).

The formed fabric was thermally bonded by compressing it through a set of two heated rolls (calenders) for improving fabric integrity and improving fabric mechanical properties. Fundamentals of the fabric thermal bonding process can be found in the review paper by Michielson et al., “Review of Thermally Point-bonded Nonwovens: Materials, Processes, and Properties”, 99 J. APPLIED POLYM. SCI. 2489-2496 (2005) or the paper by Bhat et al., “Thermal Bonding of Polypropylene Nonwovens: Effect of Bonding Variables on the Structure and Properties of the Fabrics,” 92 J. APPLIED POLYM. SCI., 3593-3600 (2004). The two rolls are referred to as “embossing” (E) and “smooth” (S) rolls. In Table 4, the set temperature of the two calenders is listed corresponding to the set oil temperature used as the heating medium of the rolls. The calender temperature was measured on both embossing and S rolls using a contact thermocouple and was typically found to be 10° C. to 20° C. lower than the set oil temperature. Under the conditions described, the spinability of the inventive compositions was assessed to be excellent.

Various polymer melt properties are reported above in Table 5 for neat and polymer blend compositions that are comparable to fiber composition used in fabric production. Without being restricted to theory, it is argued that polymer melt crystallization behavior is a factor in the fiber formation. Differences in crystallization temperatures for the various fiber components contributes in part to the generation of crimp in the fiber. Measuring crystallization temperature under shear (Tc,rheo) is an approximation of the solidification behavior for polymer composition and difference in fiber structure, ie crimp, found for fibers with bicomponent or multicomponent geometries. Further to data captured in Table 5, FIG. 1 depicts a graphical representation of complex viscosity (Pa*s) versus temperature (° C.) for fiber composition based on PP1, PP2 and PBE at various blend ratios. Similarly, FIG. 2 depicts a graphical representation of Tan Delta versus temperature (° C.) for compositions based on PP1 and PP2 and PBE at various blend ratios. Tc,rheo is determined as described above and what is surmised is that adding PBE to PP1 formulations results in a lowering of the Tc,rheo. Alternatively, adding PP2 to PP1 results in the Tc,rheo being maintained or increased over the value of Tc,rheo for PP1. Furthermore, the samples include PBE, Ex. 1 and Ex. 2, have greater contact thickness (0.55 and 0.53 mm, respectively) as compared with the contact thicknesses for Comp. Ex. 11 and Comp. Ex. 22 (0.48 and 0.43 mm, respectively), which do not include PBE. The observed improvement in thickness when incorporating PBE in the fiber composition is a function of difference created between 1^(st) and 2^(nd) fiber components.

LISTING OF EMBODIMENTS

This disclosure may further include any one or more of the following non-limiting embodiments:

-   -   1. A multicomponent fiber for nonwovens, comprising a first         fiber component comprising a first polypropylene having a MFR of         at least 30 dg/min and a second polypropylene having a MFR of         less than 20 dg/min; and a second fiber component comprising the         first polypropylene and at least one propylene-based elastomer         comprising propylene and about 10 wt % to about 30 wt % of one         or more alpha-olefin derived units, based on a total weight of         the elastomer, wherein the propylene-based elastomer has a MFR         of at least 40 dg/min and a heat of fusion (Hf) of about 3 J/g         to about 75 J/g, as determined by DSC.     -   2. The fiber according to embodiment 1, wherein the first         polypropylene has a MFR of 30 dg/min to about 40 dg/min.     -   3. The fiber according to embodiments 1 or 2, wherein the first         polypropylene has a melt temperature (Tm) of at least 140° C.     -   4. The fiber according to embodiments 1 to 3, wherein the second         polypropylene has a melt temperature (Tm) of at least 140° C.     -   5. The fiber according to embodiments 1 to 4, wherein the second         polypropylene has a MFR of 10 dg/min to about 20 dg/min.     -   6. The fiber according to embodiments 1 to 5, wherein the second         polypropylene has a MFR that is less than half the MFR of the         first polypropylene.     -   7. The fiber according to embodiments 1 to 6, wherein the second         polypropylene has a MFR that is 15% to 40% of the MFR of the         first polypropylene.     -   8. The fiber according to embodiments 1 to 7, wherein the at         least one propylene-based elastomer has a MFR of 30 dg/min to         about 60 dg/min.     -   9. The fiber according to embodiments 1 to 8, wherein the one or         more alpha-olefin derived units consist essentially of ethylene.     -   10. The fiber according to embodiments 1 to 9, wherein the one         or more alpha-olefin derived units consists of ethylene.     -   11. The fiber according to embodiments 1 to 10, wherein the at         least one propylene-based elastomer has a tacticity index (m/r)         of 4 to 12.     -   12. The fiber according to embodiments 1 to 11, wherein the at         least one propylene-based elastomer has a density of about 0.84         g/cm3 to about 0.92 g/cm3.     -   13. The fiber according to embodiments 1 to 12, wherein the at         least one propylene-based elastomer has a percent crystallinity         of about 1% to about 40%.     -   14. The fiber according to embodiments 1 to 13, wherein the         ratio of the first polypropylene to the second polypropylene in         the first fiber component ranges from 20/80 to 80/20.     -   15. The fiber according to embodiments 1 to 14, wherein a ratio         of the first polypropylene to the propylene-based elastomer in         the second fiber component ranges from 5/955/95 to 95/595/5.     -   16. The fiber according to embodiments 1 to 15, wherein the         first polypropylene is a propylene homopolymer.     -   17. The fiber according to embodiments 1 to 16, wherein herein         the second polypropylene is a propylene homopolymer.     -   18. A method for making a fiber for fabrics with suitable         thickness and softness, the method comprising: forming a first         polymer composition comprising a first polypropylene having a         MFR of at least 30 dg/min and a second polypropylene having a         MFR of less than 20 dg/min; forming a second polymer composition         comprising the first polypropylene and at least one         propylene-based elastomer comprising propylene and about 10 wt %         to about 30 wt % of one or more alpha-olefin derived units,         based on a total weight of the elastomer and having a MFR of at         least 40 dg/min and a heat of fusion (Hf) of about 3 J/g to         about 75 J/g, as determined by DSC; forming a plurality of         fibers from the first polymer composition and the second polymer         composition in a side by side configuration; and making a fabric         from the plurality of fibers, wherein the fabric has a thickness         of at least 0.40 mm, a total hand of less than 20 g, and a MD         and CD tensile of at least 8 N/5 cm.     -   19. The method according to embodiment 18, wherein forming         fibers comprises spun-bonding the first polymer composition and         the second polymer composition to form side-by-side fibers.     -   20. The method according to embodiment 18 or 19, further         comprising directing the fibers to a spin-belt, laying down the         fibers on the spin-belt and forming a fabric from the fibers.     -   21. The method according to embodiments 18 to 20, wherein a         ratio of the first polypropylene to the second polypropylene in         the first polymer composition ranges from 20/80 to 80/20, and a         ratio of the first polypropylene to the propylene-based         elastomer in the second polyer composition ranges from 5/95 to         95/5.     -   22. A hygiene product comprising the fibers of embodiments 1 to         17.

Specific embodiments of this disclosure have been described above in connection with various preferred embodiments. However, to the extent that the above description is specific to a particular embodiment or a particular use of this disclosure, this is intended to be illustrative only and merely provides a concise description of the exemplary embodiments. Accordingly, the disclosure is not limited to the specific embodiments described above, but rather, the disclosure includes all alternatives, modifications, and equivalents falling within the true scope of the appended claims. Various modifications and variations of this disclosure will be obvious to a worker skilled in the art and it is to be understood that such modifications and variations are to be included within the purview of this application and the spirit and scope of the claims.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, and/or the combination of any two upper values are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are “about” or “approximately” the indicated value, meaning the values take into account experimental error, machine tolerances and other variations that would be expected by a person having ordinary skill in the art.

The foregoing has also outlined features of several embodiments so that those skilled in the art can better understand the present disclosure. Those skilled in the art should appreciate that they can readily use the present disclosure as a basis for designing or modifying other methods or devices for carrying out the same purposes and/or achieving the same advantages of the embodiments disclosed herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure, and the scope thereof is determined by the claims that follow.

Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

1. A multicomponent fiber for nonwovens, comprising: a first fiber component comprising a first polypropylene having a MFR of at least 30 dg/min and a second polypropylene having a MFR of less than 20 dg/min; and a second fiber component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and about 10 wt % to about 30 wt % of one or more alpha-olefin derived units, based on a total weight of the elastomer, wherein the propylene-based elastomer has a MFR of at least 40 dg/min and a heat of fusion (Hf) of about 3 J/g to about 75 J/g, as determined by DSC.
 2. The fiber of claim 1, wherein the first polypropylene has a MFR of 30 dg/min to about 40 dg/min.
 3. The fiber of claim 1, wherein the first polypropylene has a melt temperature (Tm) of at least 140° C.
 4. The fiber of claim 1, wherein the second polypropylene has a melt temperature (Tm) of at least 140° C.
 5. The fiber of claim 1, wherein the second polypropylene has a MFR of 10 dg/min to about 20 dg/min.
 6. The fiber of claim 1, wherein the second polypropylene has a MFR that is less than half the MFR of the first polypropylene.
 7. The fiber of claim 1, wherein the second polypropylene has a MFR that is 15% to 40% of the MFR of the first polypropylene.
 8. The fiber of claim 1, wherein at least one propylene-based elastomer has a MFR of 40 dg/min to about 60 dg/min.
 9. The fiber of claim 1, wherein the one or more alpha-olefin derived units consist essentially of ethylene.
 10. The fiber of claim 1, wherein the one or more alpha-olefin derived units consists of ethylene.
 11. The fiber of claim 1, wherein the at least one propylene-based elastomer has a tacticity index (m/r) of 4 to
 12. 12. The fiber of claim 1, wherein the at least one propylene-based elastomer has a density of about 0.84 g/cm³ to about 0.92 g/cm³.
 13. The fiber of claim 1, wherein the at least one propylene-based elastomer has a percent crystallinity of about 1% to about 40%.
 14. The fiber of claim 1, wherein a ratio of the first polypropylene to the propylene-based elastomer in the second fiber component ranges from 5/95 to 95/5.
 15. The fiber of claim 1, wherein a ratio of the first polypropylene to the second polypropylene in the first fiber component ranges from 20/80 to 80/20.
 16. The fiber of claim 1, wherein the first polypropylene is a propylene homopolymer.
 17. The fiber of claim 1, wherein herein the second polypropylene is a propylene homopolymer.
 18. A method for making a fiber for fabrics with suitable thickness and softness, the method comprising: forming a first polymer composition comprising a first polypropylene having a MFR of at least 30 dg/min and a second polypropylene having a MFR of less than 20 dg/min; forming a second polymer composition comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and about 10 wt % to about 30 wt % of one or more alpha-olefin derived units, based on a total weight of the elastomer and having a MFR of at least 40 dg/min and a heat of fusion (Hf) of about 3 J/g to about 75 J/g, as determined by DSC; forming a plurality of fibers from the first polymer composition and the second polymer composition in a side by side configuration; and making a fabric from the plurality of fibers, wherein the fabric has a thickness of at least 0.40 mm, a total hand of less than 20 g, and a MD and CD tensile of at least 8 N/5 cm.
 19. The method of claim 18, wherein forming fibers comprises spun-bonding the first polymer composition and the second polymer composition to form side-by-side fibers.
 20. The method of claim 18, further comprising directing the fibers to a spin-belt, laying down the fibers on the spin-belt and forming a fabric from the fibers.
 21. The method of claim 18, wherein a ratio of the first polypropylene to the second polypropylene in the first polymer composition ranges from 20/80 to 80/20, and a ratio of the first polypropylene to the propylene-based elastomer in the second polymer composition ranges from 5/95 to 95/5.
 22. A hygiene product comprising the fibers of claim
 1. 23.-30. (canceled) 